Two-cycle internal combustion engine



Sept. 1, 1959 F. PORSCHE ET AL TWO-CYCLE INTERNAL COMBUSTION ENGINE Filed Aug. 28, 1956 /N VE N TOR 5 FfRD/NA ND PORS CHE AND FOBf/PT' fi/NDA'A ar 47% M47- ATTORNEYS.

United States Patent Two-CYCLE INTERNAr'coMBUsTIoN ENGINE Ferdinand Porsche, Stuttgart, Robert Binder, Stuttgart-Zulfenhausen, Germany; assignors to Fir-ma Dr. Ing. h.c.F. Prsche-KG., Stuttgart-Zuffenhausen, Ger- Application August 28', rest, stains). 606,603 1 Claims priority, application Germany'Se'p'tember 10,1955

'4 Claims. Cine-19s) The present invention relates to a two-cycle internal combustion engine provided with feed or delivery of the scavenging air into a scavenging-air chamber which surrounds the cylinder walls and from which the air passes over into the cylinder through slots or apertures controlled by the reciprocating piston.

In the known constructions of this type the scavengingair chamber is formed by the end or side walls of the cylinder block and by the cylinder liners which are inserted therein. The passage of the scavenging-air into the working space of the individual cylinders takes place through slots or apertures in the cylinder liner which are valved or controlled by the working pistons of the internal combustion engine. Such a construction exhibits the disadvantage that the removal of the combustion residues which stick to the control slots or apertures is only possible if the engine is disassembled. Furthermore, the repair and refinish'mg of the control slots, as is neces sary, for example, for an empirical determination of the most favorable dimensions thereof, requires considerable time and is connected with difficulties as a disassembly of the engine is also necessitated in that case.

According to the present invention, these disadvantages of the prior art constructions are avoided in that the air inlet slots or apertures extend through the cylinder walls as well as through the scavenging-air chamber walls and are closed by removable covers or lids. As a result thereof, the control slots or apertures are readily accessible from the outside thereof and, consequently, can be easily cleaned and machined. Furthermore, the cast parts of the engine block or of the cylinders may be kept more simple. Moreover, in a construction according to the present invention the need for a special cylinder liner for the formation of the scavenging air chamber is obviated.

Preferably, the covering of the air inlet slots or apertures is formed by a split steel band or the like. Such a covering is readily removable, simple and reliable in operation. In order to prevent effectively the inlet or escape of secondary air or of combustion gases, a heat resistant seal made, for example, of asbestos or the like is inserted between the steel band covering and the scavenging air chamber walls.

Accordingly, it is an object of the present invention to provide a construction for a two-cycle internal combustion engine which obviates the need for disassembly of the engine to clean or refinish the control apertures through which the scavenging air is admitted into the cylinders.

Another object of the present invention is the provision of such a construction of a two-cycle internal combustion engine which obviates the need for separate cylinder liners.

Still another object of the present invention resides in the provision of such a construction of two-cycle internal combustion engines which results in a compact construction in which the control slots or apertures for the admission of the scavenging air are readily accessible 2 from the outside of the cylinder and in which the scavenging-air chamber is formed integral with at least apart of the cylinder block so as to facilitate. manufacture thereof.

A further object of thepresent invention resides in the provision of a reliable covering for-the slots which may be readily removed and yet' prevent the seepage" of secondary air or combustion gases through the sealproyided thereby. I i Q These and other objects,- fea'tures and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, one preferred embodiment in accordance with the present invention and wherein Figure 1 is a central longitudinal cross-sectional view through a cylinder of an air-cooled two-cycle internal combustion engine provided with covers for the scavenging air slots according to the present invention and Figure 2 is a cross-sectional view taken along lines II-II of Figure 1.

Referring now more particularly to the drawing, wherein like reference numerals are used throughout the various views to designate like parts, reference numeral 1 designates the crankcase of the engine which is provided with a collar-like projection 2 containing an aperture or bore 3. An air-cooled cylinder 4 abuts against the projection 2. The cylinder is connected with the crankcase in any suitable manner, not illustrated herein. The cylinder is provided with an annular-shaped pocket 5 which, together with the aperture 3 of the crankcase 1, forms a scavenging-air chamber 6. The scavenging-air chamber 6 is effectively sealed against the crankcase 1 by means of a cylindrical collar 7 formed integral with the cylinder 4 which extends into the aperture or bore 3 and which is provided with a seal 8 near the inner end thereof of any suitable nature. Slots or apertures 10 are provided for the passage of the air into the cylinder space 9 which is supplied from a piston compressor or the like to the scavenging-air chamber 6, which slots or apertures 10 are controlled or valved by a piston 11. The slots 10 penetrate or extend through the outer cylinder wall 12 as well as through the scavenging-air chamber or inner cylinder wall 13 and are covered on the outside of the outer cylinder wall 12 by a split strap or clamp 15 of known construction with the insertion of a heat-resistant seal 14, made, for example, of asbestos or the like.

Upon removal of the split strap or clamp 15 and of the insulating material, which may also be in the form of a bank or strap, the slots or apertures 10 are laid bare and are readily accessible from the outside for purposes of cleaning or machining to empirically test the optimum size for a given engine without the need of disassembly of the engine itself.

The present invention is not limited to the embodiment illustrated herein but may also be used in connection with engines in which the crankcase and the cylinder are formed of a single piece.

While we have shown and described one preferred embodiment in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of many changes and modifications within the spirit of the present invention, and we intend to cover all such changes and modifications, except as defined by the appended claims.

We claim:

1. A two-cycle internal combustion engine comprising a cylinder with a lower part having integral inner and outer cylinder walls, said engine further comprising a crankcase having an annular projection with an inner wall said inner cylinder wall extending into said annular projection,

said outer cylinder wall abutting said projection, said inner cylinder Wall, said outer cylinder wall and said inner wall of said annular projection together forming a scavenging chamber, slots extending from said scavenge ing chamber through said inner cylinder wall, a piston in said cylinder to control said slots, said slots further extending through said outer cylinder wall and forming openings therein, and selectively removable cover means for said openings. 0

2. A two-cycle internal combustion engine according to claim 1, wherein said removable cover means is formed by a split clamp.

3. A two-cycle internal combustion engine according to claim 2, further comprising a heat-resistant seal inserted between the exterior of said cylinder and said split clamp.

4. A two-cycle internal combustion engine according to claim 1, wherein said selectively removable cover means for said openings is an annular member.

References Cited in the file of this patent UNITED STATES PATENTS 1,102,457 TWombly July 7, 1914 1,764,147 Burtnett June 17, 1930 2,010,170 Winfield Aug. 6, 1935 2,142,210 Rippingille Jan. 3, 1939 2,270,546 Neuland J an. 20, 1942 2,704,056 Petersen Mar. 15, 1955 2,740,390 Irgens Apr. 3, 1956 

